Anionic Substructure Research Articles

Advancing Heteroanionicity in Zintl Phases: Crystal Structures, Thermoelectric and Magnetic Properties of Two Quaternary Semiconducting Arsenide Oxides, Eu8Zn2As6O and Eu14Zn5As12O.

Two novel quaternary oxyarsenides, Eu8Zn2As6O and Eu14Zn5As12O, were synthesized through metal flux reactions, and their crystal structures were established by single-crystal X-ray diffraction methods. Eu8Zn2As6O crystallizes in the orthorhombic space group Pbca, featuring polyanionic ribbons composed of corner-shared triangular [ZnAs3] units, running along the [100] direction. The structure of Eu14Zn5As12O crystallizes in the monoclinic space group P2/m and its anionic substructure can be described as an infinite "ribbonlike" chain comprised of [ZnAs3] trigonal-planar units, although the structural complexity here is greater and also amplified by disorder on multiple crystallographic positions. In both structures, the O2- anion occupies an octahedral void with six neighboring Eu2+ cations. Formal electron counting, electronic structure calculations, and transport properties reveal the charge-balanced semiconducting nature of these heteroanionic Zintl phases. High-temperature thermoelectric transport properties measurements on Eu14Zn5As12O reveal relatively high resistivity (ρ500K = 8 Ω·cm) and Seebeck coefficient values (S500K = 220 μV K-1), along with a low concentration and mobility of holes as the dominant charge-carriers (n500K = 8.0 × 1017 cm-3, μ500K = 6.4 cm2/V s). Magnetic studies indicate the presence of divalent Eu2+ species in Eu14Zn5As12O and complex magnetic ordering, with two transitions observed at T1 = 21.6 K and T2 = 9 K.

Ba5Sb8: The Highest Homologue of the Family of Binary Semiconducting Barium Antimonides BanSb2n−2 (n ≥ 2)

A novel binary compound within the Ba–Sb phase diagram, Ba5Sb8, was synthesized by combining elements with an excess of Sb in an alumina crucible. Structural elucidation was performed using single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic space group Fdd2 with unit cell parameters of a = 15.6568(13) Å, b = 35.240(3) Å, c = 6.8189(6) Å, adopting its own structure type. The most distinctive features of the structure are the eight-membered [Sb8]10− polyanionic fragments which have no known precedents among antimonides. They are separated by five Ba2+ cations, which afford the charge balance and enable adherence to the Zintl–Klemm formalism. Ba5Sb8 is the highest known member of the homologous series within the family of barium antimonides BanSb2n−2 (n ≥ 2), all of which boast anionic substructures with oligomeric moieties of pnictogen atoms with varied lengths and topologies. Electronic structure calculations indicate an indirect narrow bandgap of ca. 0.45 eV, which corroborates the valence-precise chemical bonding in Ba5Sb8.

TO A QUESTION OF SULFUR SITES IN CRYSTAL STRUCTURES OF TETRAHEDRITE GROUP MINERALS: RELATIONSHIPS BETWEEN OCCUPANCY, EFFECTIVE ION SIZES, AND UNIT CELL PARAMETERS

In this work, a crystal chemical analysis of the known experimentally deciphered crystal structures of tetrahedrite group minerals was carried out in order to reveal the relationships between the occupancies of anion crystallographic sites in the structures, their effective sizes and unit cell parameters. To achieve this aim, we analyzed the effective sizes of the 24g and 2a anion sites in 68 deciphered crystal structures of tetrahedrite group minerals according to the published data. The analysis was carried out using the TOPOSPro software package by partitioning the space into Voronoi–Dirichlet polyhedra (VDP). It has been shown theoretically for the first time that the content of a large sulfur ion and its deficiency affect the unit cell parameter. A linear correlation between the VDP volume of the anionic site of S2– (24g) and the unit cell parameter in minerals of the tetrahedrite group was established, which shows that the anionic substructure dictates the structural motif in this class of compounds. It was found that the change in the VDP volumes of sulfur anions is associated with different occupancies of anionic sites. It is found that the formula (unit cell) of the compound contains fewer than 13 sulfur ions in almost all deciphered crystal structures of tetrahedrite group minerals. It was concluded that the calculated VDP volume of the 24g anionic position less than 22 Å3 indicates a significant deficit in the anionic substructure. It was shown that, using information about the VDP volumes of all anionic and cationic sites in the structure, it is possible to predict the unit cell parameters of minerals of the tetrahedrite group with an accuracy of 0.01 Å

A small-box approach to the local crystal structure of Y3NbO7

The local crystal structure of Y3NbO7 was probed using neutron total scattering. Five different structural models were fit to the experimental pair distribution function of this material up to 15 Å. Fits of defect fluorite (Fm3‾m), pyrochlore (Fd3‾m), and orthorhombic C weberite models (C2221) were attempted based on prior structural investigations of Y3NbO7 and related fluorite-based materials. Orthorhombic P weberite (P2221) and monoclinic weberite models (P1121) were derived via symmetry reduction of the orthorhombic C weberite structure. All models except monoclinic weberite failed to reproduce the experimental pair distribution function. Misfits were clearly visible for peaks arising from atom pairs within the first coordination shell (defect fluorite and pyrochlore) and beyond (orthorhombic C and P weberite). By contrast, monoclinic weberite (γ ≈ 91.8°) provided an excellent fit, with no major misfits observed. This unit cell features distorted YO8 dodecahedra, YO7 monocapped octahedra, and NbO6 octahedra as building blocks. Comparison between the topologies of the cationic and anionic substructures in monoclinic weberite and its parent orthorhombic C structure revealed displacements of the metal atoms along the [100] direction and a less compact spatial distribution of oxygen atoms along the a axis. The monoclinic weberite model presented herein may serve as a starting point to revisit structural modeling of fluorite-based materials with challenging local structures.

Ion-Selective Assembly of Supertetrahedral Selenido Germanate Clusters for Alkali Metal Ion Capture and Separation

Supertetrahedral chalcogenido (semi)metalate cluster-based frameworks possess high selectivity for alkali metal cations, matching the specific charge density of their inner surfaces, which enables their use as ion-exchange materials. Aggregates of the supertetrahedral chalcogenido metalate cluster offer even new perspectives for metal ion capture and separation. Herein, we report on ionothermal preparation of two corresponding model compounds, (C2C1Im)7[Cs@GeII4(GeIV4Se10)4] (1) and (C2C1Im)10[Na5(CN)6@Cu6(Ge4Se10)4(Cu)] (2). Their formation is reliant on one specific cation type each, Cs+ for 1 and Na+ for 2, thus providing promising separation potential during crystallization. Compound 1 is based on the largest discrete binary selenido germanate cluster reported to date and the first mixed-valent chalcogenido germanate(II/IV) supertetrahedron. Moreover, it adds to the few examples of chalcogenides capable of capturing Cs+ ions. Its high selectivity for Cs+ compared to that of Li+, Na+, K+, and Rb+ was confirmed by single-crystal X-ray diffraction, energy-dispersive X-ray spectroscopy, and electrospray ionization mass spectrometry. Quantum chemical studies indicate that smaller ions, K+ and Rb+, could also be embedded in an isolated cluster assembly, but as the cluster aggregate slightly distorts for crystallization, the selectivity for Cs+ becomes exclusive in the salt. The anionic substructure of compound 2 is based on a two-dimensional network of supramolecular assemblies and exhibits an exclusive preference for Na+. This work thus provides the first comprehensive insight into the selective incorporation of specific alkali metal ions into supramolecular aggregates of supertetrahedral chalcogenide clusters, as a promising basis for new ion trapping techniques─especially for heavy alkali metal ions that pose environmental challenges.

Screening Order–Disorder Phase Transition in 1-D Perovskite-like Crystals of [Azetidinium]CdBr3

In search for new polar compounds, we have synthesized the organic–inorganic hybrid [C3H8N]CdBr3 (AZECdBr3). This is a bromide analog of [C3H8N]CdCl3, which has been studied by us earlier. The chloride compound exhibited ferroelectric properties, so it seemed reasonable to check the properties of AZECdBr3. The AZECdBr3 crystals reveal three phase transitions (PTs): the first one (I → II) of the second order at 437.0/436.7 K (heating/cooling), the next (also of the second order) at 231.0 K (II → III), and the last one (classified as a first-order transition) at 197.0/194.0 K (III → IV). On the basis of the DSC data, the thermodynamic parameters have been estimated. The single-crystal X-ray measurements indicate orthorhombic symmetry in all phases investigated, i.e., space groups: Cmcm (phase II 250.0(1) K) and Pbnm for structures at 215.0(1) K (phase III) and 100.0(1) K (phase IV). The anionic substructure is composed of distorted [CdBr6]4– octahedra forming infinite one-dimensional [{CdBr3}−]n chains arranged in the c-direction. The azetidinium cations, C3H8N+, are located between these inorganic chains. The dielectric permittivity, ε′, measured at frequencies from the range between 500 Hz and 2 MHz obtained for single crystals along the [100], [010], and [001] directions evidenced a strong anisotropy. The ferroelastic nature of phases II, III, and IV was confirmed by the polarized light microscopy photographs. On the basis of the obtained results, the mechanisms of the solid–solid PTs have been proposed.

Impact of structure complexity on optoelectronic and non-linear optical properties in quaternary Ag(Pb)–Ga(In)–Si(Ge)–S(Se) systems

A common feature of chalcogenide crystals is the presence of the chalcogen-chalcogen bonds, which result in very stable anion sub-structures (blocks) containing up to eight chalcogenide ions with the electric charge − 2 in units of the proton charge like systems [PS4]3-, [SiS4]4-, [GeS4]4-, [GeSe5]4-, [Ge2Se6]6-. The size of anion blocks, their mutual arrangement and chemical bonds between them consequently determine the optical and detection properties. By modifying the chemical composition with subsequent use of the laser irradiation, it is possible to change crystal optoelectronic properties in a wide spectral range. In the work, we discuss the influence of the structural properties on the stability, electronic, optical and nonlinear-optical efficiency for the group of quaternary chalcogenide crystals with Ag(Pb)–Ga(In)–Si(Ge)–S(Se) composition, that have already found practical applications in IR optoelectronics and non-linear optics. The presented analysis of chemical composition-structure - nonlinear optical properties relationship can be useful for the creation of effective quaternary crystals for nonlinear optics application.

Synthesis and characterization of amantadinium iodoacetatobismuthate, a hybrid compound with mixed iodide–carboxylate anions

The amantadinium iodoacetatobismuthate(III) [C10H15NH3·(CH3)2CO]2[BiI3.67(CH3COO)1.33] is a new hybrid halometallate with iodide ions partially replaced by oxygen-containing acetates to form stronger interaction between the anionic and cationic substructures. The title compound as well-shaped orange-red crystals was synthesized by a facile reaction in acetone solution in the presence of glacial acetic acid. The crystal structure of the compound consists of the infinite anionic chains [BiI3.67(CH3COO)1.33]2– and the countercations [C10H15NH3·(CH3)2CO]+; according to the optical absorption data, the test compound is a semiconductor with a band gap of 2.06 eV.

Be[B2(SO4)4] – A Borosulfate Exhibiting Ino‐ and Phyllosilicate Analogue Topology

AbstractBorosulfates are a constantly expanding class of silicate analogue compounds. The anionic substructures are composed of vertex‐connected (BO4)‐ and (SO4)‐tetrahedra and feature topologies of monomeric, oligomeric, and polymeric anions. The latter resemble typical motifs of ino‐, phyllo‐ and tectosilicates but none of the hitherto known borosulfates exhibits two different anion topologies within one structure. However, this is very rare even for the homopolyanionic silicates. Be[B2(SO4)4] is the first borosulfate featuring anionic chains and layers within one structure and both substructures are interconnected by (BeO4)‐tetrahedra. DFT calculations complement the experimental studies and help to describe the bonding situation of the Be−O bonds.

A mixed-valence copper chloride coordination polymer composed of one-dimensional cationic and anionic substructures

A coordination polymer composed of cationic [CuIICl2(Hdatrz)2]2+ and anionic [CuI2Cl4]2− substructures was obtained from the reaction of 3,5-diamino-1,2,4-triazole (datrz) with CuICl and CuIICl2 in the presence of HCl.

Synthesis and structural characterization of the new Zintl phases Eu10Mn6Bi12 and Yb10Zn6Sb12.

Two new ternary compounds, Eu10Mn6Bi12 and Yb10Zn6Sb12, were synthesized and structurally characterized. The synthesis was achieved either through reactions in sealed niobium tubes or in alumina crucibles by combining the elements in excess molten Sb. Their structures were elucidated using single-crystal X-ray diffraction, and they were determined to crystallize in the orthorhombic space group Cmmm (no. 65) with the Eu10Cd6Bi12 structure type. Akin to the archetype phase, both Mn and Zn sites contain about 25% of vacancies. The anionic substructure of the title phases can be described as [M6Pn12] (M = Zn, Mn; Pn = Sb, Bi) double layers composed of the corner and edge-sharing [MPn4] tetrahedra, linked by [Pn2]4- dumbbells. Eu2+/Yb2+ cations fill the space between the layers, with the valence electron counts adhering closely to the Zintl-Klemm rules, i.e., both Eu10Mn6Bi12 and Yb10Zn6Sb12 are expected to be valence-precise compounds. Analysis of the electronic structure and transport properties of Yb10Zn6Sb12 indicate semimetallic behavior with relatively low Seebeck coefficient and resistivity that slightly decreases as a function of temperature.

Ionothermal Access to Defined Oligomers of Supertetrahedral Selenido Germanate Clusters.

Supertetrahedral chalcogenido (semi)metalate clusters have been in the focus of inorganic and materials chemistry for many years owing to a variety of outstanding physical and chemical properties. However, a critical drawback in the canon of studying corresponding compounds has been the lack of control in assembling the supertetrahedral units, which have been known as either highly charged monomeric cluster anions or lower charged, yet extended anionic substructures of linked clusters. The latter is the reason for the predominance of applications of such materials in heterogeneous environment, or their solubilization by organic shielding, which in turn was unfavorable regarding the optical properties. Recently, we reported a partial alkylation of such clusters, which allowed for a significantly enhanced solubility at a marginal impact on the optical gap. Herein we showcase the formation of finite cluster oligomers of supertetrahedral architectures by ionothermal syntheses. We were successful in generating the unprecedented dimers and tetramers of the [Ge4Se10]4– anion in salts with imidazolium-based ionic liquid counterions. The oligomers exhibit lower average negative charges and thus reduced electrostatic interactions between anionic clusters and cationic counterions. As a consequence, the salts readily dissolve in common solvents like DMF. Besides, the tetrameric [Ge16Se36]8– anion represents the largest discrete chalcogenide cluster of a group 14 element. We prove that undestroyed cluster oligomers can be transferred into solution by means of electrospray ionization (ESI) mass spectrometry and provide a full set of characteristics of the compounds including crystal structures and optical properties.

Ino-Chloridolithates from Ionothermal Synthesis

Anionic lithium-containing species were predicted to impact ionic liquid-based electrochemical applications but have hitherto never been isolated from ionic liquid systems. Here, we report the first representatives of this class of compounds, ino-chloridolithates, comprising [LiCl2]- and [Li2Cl3]- polyanions from ionothermal reactions. Such compounds are obtained at moderate temperatures with imidazolium-based ionic liquids and LiCl. The addition of an auxiliary ammonium salt enhances the lattice energy to yield an ammonium lithate in good yields, which enables extensive investigations including solid-state nuclear magnetic resonance, infrared, and Raman spectroscopy. The structural motifs of ino-lithates are related to ino-silicates, as 1D-extended anionic substructures are formed. Despite this analogy, according to density functional theory calculations with periodic boundary conditions, no evidence of covalent bonding in the anionic moieties is found-indicating packing effects to be the main cause for the formation. Based on an in-depth analysis of the different synthetic parameters, this class of compounds is discussed as an intermediate in ionic liquid applications and could serve as a model system for electrochemical lithium-based systems.

0D Bismuth(III)-Based Hybrid Ferroelectric: Tris(acetamidinium) Hexabromobismuthate(III)

Ferroelectric properties of haloantimonates(III) and halobismuthates(III) have been detected for as much as 40 structures belonging to 7 different types of anionic networks, with RMX4, R2MX5, R3M2X9, and R5M2X11 stoichiometries being the most frequently reported to host these properties. We report on the first ferroelectric of the halobismuthate(III) family with a R3MX6 stoichiometry, that is, tris(acetamidinium)hexabromobismuthate(III), (CH3C(NH2)2)3[BiBr6] (ABB), characterized by a one-component organic network. While the stoichiometry and crystal packing of ABB might seem uncomplicated, the temperature-resolved structural and spectroscopic studies paint a different picture in which rich polymorphism in the solid state occurs between tetragonal (paraelastic) and triclinic (ferroelastic) crystal phases: I (P42/n) → II (P1̅) at 272/277 K (cooling/heating), II (P1̅) → III (P1̅) at 207 K, and III (P1̅) → IV (P1) at 98/127 K. The ferroelectric properties of phase IV have been confirmed by the pyroelectric current and hysteresis loop measurements; additionally, the acentric symmetry has been further supported by second harmonic generation measurements. Crystallographic analysis of phase III reveals the antiparallel alignment of acetamidinium dipoles, pointing to the antiferrroelectric nature of this phase. In turn, the character of the ferroelectric transition (III → IV) should be considered as “displacive” for both cationic and anionic substructures.) In this report, we also explore the two-photon absorption property of ABB at 800 nm, a property that is unexplored for any halobismuthate(III) thus far. We also present periodic ab initio calculations for ABB crystals. The Berry-phase approach at the Hartree–Fock and density functional theory (DFT-D3) method levels is employed for spontaneous polarization calculations. The origin of ferroelectric polarization is studied using DFT-D3 and RHF electronic structure calculations, emphasizing the relationship between Ps and the relative orientation of organic/inorganic components.

Ion Dynamics and Polymorphism in Cu20Te11Cl3.

Coinage metal polychalcogenide halides are an intriguing class of materials, and many representatives are solid ion conductors and thermoelectric materials. The materials show high ion mobility, polymorphism, and various attractive interactions in the cation and anion substructures. Especially the latter feature leads to complex electronic structures and the occurrence of charge-density waves (CDWs) and, as a result, the first p-n-p switching materials. During our systematic investigations for new p-n-n switching materials in the Cu-Te-Cl phase diagram, we were able to isolate polymorphic Cu20Te11Cl3, which we characterized structurally and with regard to its electronic and thermoelectric properties. Cu20Te11Cl3 is trimorphic, with phase transitions occurring at 288 and 450 K. The crystal structures of two polymorphs, the α phase, stable above 450 K, and the β polymorph (288-450 K), are reported, and the complex structure chemistry featuring twinning upon a phase change is illustrated. We identified a dynamic cation substructure and a static anion substructure for all polymorphs, characterizing Cu20Te11Cl3 as a solid Cu-ion conductor. Temperature-dependent measurements of the Seebeck coefficient and total conductivity were performed and substantiated a linear response of the Seebeck coefficient, a lack of CDWs, and no p-n-p switching. Reasons for a lack of CDWs in Cu20Te11Cl3 are discussed and illustrated in the context of existing p-n-p switching materials.

Understanding distortions of inorganic substructures in chloridobismuthates(III)

The molar ratio variations of organic and inorganic reactants of chloridobismuthates(III) with N,N-dimethylethane-1,2-diammonium, [(CH3)2NH(CH2)2NH3]2+, and N,N,N′,N′-tetramethylguanidinium, [NH2C{N(CH3)2}2]+, cations lead to the formation of four different products, namely, tris(N,N-dimethylethane-1,2-diammonium) bis[hexachloridobismuthate(III)], [(CH3)2NH(CH2)2NH3]3[BiCl6]2 (1), catena-poly[N,N-dimethylethane-1,2-diammonium [[tetrachloridobismuthate(III)]-μ-chlorido]], {[(CH3)2NH(CH2)2NH3][BiCl5]} n (2), tris(N,N,N′,N′-tetramethylguanidinium) tri-μ-chlorido-bis[trichloridobismuthate(III)], [NH2C{N(CH3)2}2]3[Bi2Cl9] (3), and catena-poly[N,N,N′,N′-tetramethylguanidinium [[dichloridobismuthate(III)]-di-μ-chlorido]], {[NH2C{N(CH3)2}2][BiCl4]} n (4). The hybrid crystals 1–4, containing relatively large but different organic cations, are composed of four distinct anionic substructures. They are built up from isolated [BiCl6]3− octahedra in 1, from face-sharing bioctahedral [Bi2Cl9]3− units in 3, from polymeric corner-sharing {[BiCl5]2−} n chains in 2 and from edge-sharing {[BiCl4]−} n chains in 4. The distortions shown by the single [BiCl6]3− polyhedra in 1–4 are associated with intrinsic interactions within the anionic substructures and the organic...inorganic substructures interactions, namely, N/C—H...Cl hydrogen bonds. The first factor is the stronger, which is evident in comparison of the experimentally determined geometrical and calculated distortion parameters for the isolated octahedron in 1 to the more complex inorganic substructures in 2–4. The formation of N—H...Cl hydrogen bonds, in terms of their number and strength, is favoured for 1 and 3 containing relatively easily accessed hydrogen-bond acceptors of isolated [BiCl6]3− and [Bi2Cl9]3− units. The studies of the deviations from regularity of the [BiCl6]3− octahedra within inorganic substructures were supported by a survey of the Cambridge Structural Database, which confirmed the role played by different factors in the variations in geometry of the inorganic anions.

Architecture of hydrogen-bonded anionic substructure versus cation type in thiazolium hypodiphosphates

Architecture of hydrogen-bonded anionic substructure <i>versus</i> cation type in thiazolium hypodiphosphates

Inside Back Cover: Triple‐Vertex Linkage of (BO4)‐Tetrahedra in a Borosulfate: Synthesis, Crystal Structure, and Quantum‐Chemical Investigation of Sr[B3O(SO4)4(SO4H)] (Angew. Chem. Int. Ed. 36/2021)

A synthesis to control the amount of reacting SO3 and the cation to boron ratio during solvothermal syntheses with oleum is crucial to explore the structural diversity of borosulfates. The novel borosulfate Sr[B3O(SO4)4(HSO4)] was synthesized in phase-pure form, and the anionic substructure features a triple-vertex connection of three (BO4) tetrahedra via one oxygen atom. The motif was previously unknown for borosulfates, but is not uncommon for borates. This outperformance of silicate-untypical behavior of a borosulfate was further investigated by means of DFT calculations, as reported by Jörn Bruns and co-workers in their Communication on page 19740.

Triple-Vertex Linkage of (BO4 )-Tetrahedra in a Borosulfate: Synthesis, Crystal Structure, and Quantum-Chemical Investigation of Sr[B3 O(SO4 )4 (SO4 H)

Borosulfates are classified as silicate analogue materials. The number of crystallographically characterized compounds is still limited, whereas the structural diversity is already impressive. The anionic substructures of borosulfates exhibit vertex‐connected (BO4)‐ and (SO4)‐tetrahedra, whereas bridging between two (SO4)‐ or even between two (BO4)‐tetrahedra is scarce. The herein presented compound Sr[B3O(SO4)4(SO4H)] is the first borosulfate with a triple‐vertex linkage of three (BO4) tetrahedra via one common oxygen atom. DFT calculations complement the experimental studies. Bader charges (calculated for all atoms) as well as charge‐density calculations give hint to the electron distribution within the anionic substructure and density‐of‐states calculations support the interpretation of the bonding situation.

Ammonothermal Synthesis and Characterization of First Amidozincate Hydroxides

AbstractThe first alkali metal amidozincate hydroxides Na3[Zn(NH2)4](OH) and Na3[Zn(NH2)3](OH)2were obtained from supercritical ammonia under ammonobasic conditions at 823 K and 250 MPa, and 623 K and 159 MPa, respectively. Crystal structures have been refined against single crystal X‐ray diffraction intensity data. Coordination environments of the cations as well as the rather open crystal structure and low density of Na3[Zn(NH2)4](OH) suggest the initial formation of a monoammoniate, prior loss of ammonia during depressurizing and recovery of the product. While Na3[Zn(NH2)4](OH) contains mutually isolated amidozincate ions next to hydroxide ions, Na3[Zn(NH2)3](OH)2is the first amidozincate realizing a condensation of the complex anionic substructure so far. Both compounds are regarded possible intermediates in an ammonothermal zinc nitride synthesis and give insights into the action of impurities during ammonothermal processes. Raman spectroscopic measurements support the assignment of amide and hydroxide groups.